It’s more subtle than that. “Toxic” is used as a synonym for “irredeemably harmful”, and that very distinction makes all the difference. If a person is labeled a “jerk”, they are potentially redeemable and able to be reformed, but if someone is labeled as “toxic”, the label itself declares that there is no helping them. The label itself prescribes ostracism.
So, while it is indeed free of connotations of intent, it evokes disgust and, in fact, invites ostracism. If something is so dangerous that it can kill you, there's rarely much wisdom in attempting to talk it out of being lethal. Better to just remove it from your environment.
In any case, I agree that the word is tragically overworked. And don't we all know that overwork can be toxic.
I am non-contact with a toxic parent because I know it brings out worse behaviour in myself, and I want to stop that cycle of passive-aggressiveness and judgement towards people I do care about.
I just meant to say that *to me*, toxic doesn't imply irredeemable. It's just a popular word for harmful.
So really I think "toxic" is appropriate.